/*!
* \file sfinae.h
* \brief Template meta-programming SFINAE helpers
*
* Copyright (C) 2018 Christos Choutouridis
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU Lesser General Public License as
* published by the Free Software Foundation, either version 3
* of the License, or (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public License
* along with this program. If not, see .
*/
#ifndef __utl_meta_sfinae_h__
#define __utl_meta_sfinae_h__
#include
/*!
* \ingroup meta
* \defgroup sfinae
* conditional use support header.
*/
//! @{
namespace utl {
namespace meta {
//! Tool to enable a partial specialization only if a boolean condition is true.
//! @{
namespace detail {
template
struct dev_null { using type = dev_null; }; //< Same as typelist
template struct when_ { };
template <> struct when_ { using type = void; };
}
//! Well formed only if \p If is true
template
using when = type_>;
//! Well formed only if all of \p Ifs are \c true
template
using when_all = detail::dev_null<
when...
>;
//! @}
//! select _Tp if \p If is true, else SFINAE
//! We implement eneble_if so we don't have to pull entire \c from stl
//! @{
template
struct enable_if {
using type = _Tp;
};
template
struct enable_if { /* SFINAE*/ };
//! Alias template for enable_if
template
using use_if = enable_if;
//! Publicly recognized alias template for enable_if
template
using enable_if_t = type_<
enable_if
>;
//! Uniform alias template for use_if
template
using use_if_t = type_<
enable_if
>;
//! @}
}}
//! @}
#endif /* __utl_meta_sfinae_h__ */